Seed germination control through mitochondrial thiol switches

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Seeds are our main food source. For plants, seeds allow propagation over long distances and time periods, and provide protection of progeny from hostile environments, such as cold or drought. The remarkable ability of a seed to preserve a preformed embryo in a quiescent state and to rapidly re-activate it when the conditions are favourable is unique to higher plants. During germination the embryo relies on the energy stores within the seed. Their rapid mobilization to provide the ATP that the cells require for efficient germination is critically dependent on the mitochondria. While mitochondrial metabolism has to be largely inactive during quiescence to preserve resources, activation of germination at imbibition necessitates a sharp and rapid kick-start. As part of this wakeup call, numerous protein thiol switches are rapidly operated and germination efficiency depends on the mitochondrial glutathione and thioredoxin machineries. In this project we aim to dissect the specificity and regulatory significance of different mitochondrial thiol switches in controlling and supporting germination of Arabidopsis thaliana. A tailored in situ sensing setup for subcellular redox and energy physiology in intact seeds, embryos and purified mitochondria will allow to monitor the rapid transition in thiol redox status and its crosstalk with cellular energy physiology. Sensing will inform state-of-the-art quantitative thiol redox proteomics to elucidate the identity and specificity of the individual target protein thiol switches, which are operated under the endogenous thermodynamic and kinetic constraints. Their individual regulatory significance and specificity will be dissected using targeted cysteine mutagenesis, in silico interaction modelling, as well as respiratory, metabolic and protein biochemical analyses. The implications that operation of mitochondrial thiol switches has on seed vigour and germination control will be investigated in the context of seed dormancy and aging. As such this work will elucidate the significance of mitochondrial thiol switching as an upstream mechanism of germination control.